drm/rockchip: vop: fix mask when updating interrupts

Commit dbb3d944

 (drm/rockchip: vop: move interrupt registers into
vop_data) introduced new macros for updating the interrupt control
registers but these always use the mask from the register definition
without refining it for the particular bits that are being changed.

This means that whenever we enable/disable a particular interrupt we end
up disabling all of the others as a side effect.

Signed-off-by: John Keeping <john@metanate.com>